MONACO (AP) Australian driver Daniel Ricciardo gave improving Red Bull another boost Thursday with the fastest time in the second practice session of the Monaco Grand Prix, ahead of Mercedes pair Lewis Hamilton and Nico Rosberg.
Red Bull struggled for consistency last season, and came close to cutting ties with engine supplier Renault, but the car's pace is clearly improving.
Teammate Max Verstappen won the Spanish GP two weeks ago, and Ricciardo was more than half a second quicker than Hamilton and .899 seconds faster than Rosberg, with Verstappen fourth quickest.
''I have good confidence with the car. We have a bit more downforce than other cars so that keeps us a bit steadier,'' Ricciardo said. ''The chassis is good and we've found some good time.''
However, Ricciardo remains wary of how much Mercedes might be holding back for Saturday's qualifying.
''I'll be surprised if we can keep that gap in qualifying,'' Ricciardo said. ''I know they always have a little bit more for qualifying, they're able to get a bit more power out of the engine.''
Rosberg, who won the first four races of the year to take a commanding lead in the championship, felt frustrated.
''The sessions were a bit messy, with quite a few virtual safety car periods,'' Rosberg said. ''We have some more homework to do but I can't wait for the qualifying battle. It should be very close and very exciting.''
In the morning's first practice, Hamilton led Rosberg by .101, with Ferrari driver Sebastian Vettel third quickest.
Vettel struggled badly in the afternoon, however, damaging his rear wing at the Mirabeau turn and spinning his car at Sainte Devote as he clocked the ninth fastest time.
''It was a bit of a scrappy day. It's fair to say that just inside the top 10 is not where we belong,'' the four-time F1 champion said. ''In the end it's my fault if I go in too deep and touch the barrier.''
The Monaco GP has no action on Friday - unique in F1 - and there is a final practice Saturday ahead of qualifying.
''Saturday is when it matters,'' said Vettel, who won in Monaco driving for Red Bull in 2011. ''There's a lot of stuff we learned today.''
Like Vettel, Hamilton has also only won the Monaco GP once, with McLaren in 2008.
The British driver had a frustrating race last year when late team orders to pit, after a safety car was deployed following a crash, saw him slip from first to third behind Vettel and Rosberg - who won for the third straight year.
Chasing a third straight title and fourth overall, Hamilton trails Rosberg by 43 points and has gone eight races without a win since sealing the championship at the United States GP with three races to spare.
Hamilton made the early afternoon running on the super-soft tire compound, but Ricciardo made full use of the upgraded Renault engine and the even faster ultra-softs to zoom up the leaderboard.
It will do wonders for Ricciardo's confidence.
He won three races in his first season with Red Bull in 2014, stepping in for Vettel when he joined Ferrari, but has not finished on the podium in 11 races. This season, he has finished fourth four times and placed a lowly 11th at the Russian GP.
Both practice sessions were eventful.
In the second, French driver Romain Grosjean lost part of the front wing on his Haas car after clipping the barrier coming out of the tunnel, while late in the first Rosberg picked up a puncture after running over a loose drain cover.
The cover clipped Jenson Button's McLaren, damaging the front wing and halting the session.
Meanwhile, Williams watched in frustration as veteran driver Felipe Massa lost control turning up the hill at Sainte Devote and slammed into the barrier, damaging the left side of his car.